Charm production in the forward region: constraints on the small-x gluon and backgrounds for neutrino astronomy
Charm production in the forward region: constraints on the small-x gluon and backgrounds for neutrino astronomy
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DOI：
10.1007/jhep11(2015)009
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发表时间：
2015-06
影响因子：
5.4
通讯作者：
R. Gauld;J. Rojo;L. Rottoli;Jim Talbert
中科院分区：
文献类型：
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作者：
R. Gauld;J. Rojo;L. Rottoli;Jim Talbert
最近，冰立方实验对能量高达几个PeV的宇宙中微子的观测预示着中微子天文学的开始。在如此高的能量下，“常规”中微子通量被抑制，来自Charm介子衰变的“瞬发”分量有望成为天体物理中微子的主要背景。然而，高能下的魅力产生在理论上是不确定的，这既是因为NLO计算的尺度不确定性很大，也是因为它对小x处鲜为人知的胶子PDF直接敏感。在这项工作中，我们提供了详细的微扰QCD预测的魅力和底部生产的正向区域，并通过比较最新的数据从LHCb实验在7TeV。在数据和理论之间找到了很好的一致性，我们使用LHCb测量来约束小x胶子PDF，实现了它的不确定性的显著减少。使用这些改进的PDF，我们预测了LHCb在13TeV时的魅力和底部产量，以及13和7TeV之间的横截面比率。同样的计算也被用于计算PA碰撞中魅力衰变产生的中微子的能量分布，这是实现对中微子望远镜魅力诱导背景的理论上可靠估计的关键因素。
The recent observation by the IceCube experiment of cosmic neutrinos at energies up to a few PeV heralds the beginning of neutrino astronomy. At such high energies, the ‘conventional’neutrino flux is suppressed and the ‘prompt’component from charm meson decays is expected to become the dominant background to astrophysical neutrinos. Charm production at high energies is however theoretically uncertain, both since the scale uncertainties of the NLO calculation are large, and also because it is directly sensitive to the poorly-known gluon PDF at small-x. In this work we provide detailed perturbative QCD predictions for charm and bottom production in the forward region, and validate them by comparing with recent data from the LHCb experiment at 7 TeV. Finding good agreement between data and theory, we use the LHCb measurements to constrain the small-x gluon PDF, achieving a substantial reduction in its uncertainties. Using these improved PDFs, we provide predictions for charm and bottom production at LHCb at 13 TeV, as well as for the ratio of cross-sections between 13 and 7 TeV. The same calculations are used to compute the energy distribution of neutrinos from charm decays in pA collisions, a key ingredient towards achieving a theoretically robust estimate of charm-induced backgrounds at neutrino telescopes.